Nowadays, owing to such advantages as light weight, thin profile, low power consumption and low radiation, liquid crystal display (LCD) devices have found wide application in various electronic products such as computer monitors, TV sets, notebook computers, mobile phones, digital cameras and the like.
Referring to FIG. 1, there is shown a schematic circuit diagram of an LCD device in the prior art. As shown in FIG. 1, the prior art LCD device 10 comprises a liquid crystal panel 100. The liquid crystal panel 100 comprises a plurality of scan lines 111 parallel with each other and a plurality of data lines 112 parallel with each other. The scan lines 111 and the data lines 112 intersect with and are insulated from each other to define a plurality of pixel units 101.
Each of the pixel units 101 comprises a thin film transistor (TFT) 102, a storage capacitor 103 and a liquid crystal capacitor 104 all disposed at an intersection of a scan line 111 and a data line 112.
The TFT 102 has a gate electrically connected to the scan line 111, a source electrically connected to the data line 112 and a drain electrically connected to an end of the storage capacitor 103. The liquid crystal capacitor 104 and the storage capacitor 103 are electrically connected in parallel.
The LCD device 10 further comprises a backlight source (not shown) disposed beneath the liquid crystal panel 100 to provide necessary backlight for the liquid crystal panel 100. In practice, white light sources with a continuous spectrum are known as a kind of commonly used backlight source. However, in order to save energy and lower the cost, the Field-sequential-color (FSC) mechanism has been proposed in the prior art. According to the FSC mechanism, a scanning FSC backlight source employing separate RGB-LEDs is used to replace the conventional white light source with a continuous spectrum, and the RGB LEDs are used as a backlight source to emit light of different colors in place of a color filter. Because the need of a color filter is eliminated, this can lower the manufacturing cost of the LCD device, reduce the light loss rate and the power consumption, and improve the light emission efficiency.
Specifically, in order to drive the prior art LCD device 10, a scan signal is inputted at first to the scan lines 111 to sequentially scan the gate of the TFT 102 of each pixel unit 101 so that the TFT 102 is turned on and then transfer a data signal via the data line 112 to the storage capacitor 103 and the liquid crystal capacitor 104. The liquid crystal capacitor 104 supplies a voltage for tilting liquid crystal molecules. Then, after the liquid crystal molecules have tilted to a predetermined orientation, the backlight is turned on.
More specifically, because RGB LEDs are used to generate light of different colors in FSC LCD, the RGB LEDs must be turned on sequentially section by section. Each section comprises a number of scan lines 111, and gates of the TFTs 102 electrically connected with these scan lines 111 are turned on sequentially in one frame. After the gates are turned on, the liquid crystal molecules are tilted to cause optical changes.
Accordingly, in the prior art, all gates of TFTs in each section are turned on, and the backlight cannot be turned on until the liquid crystal molecules tilt to the predetermined orientation. Because this shortens the time duration in which the backlight can be turned on, the number of LEDs must be increased to achieve a desired brightness level, thus leading to a higher cost.